L\xc3\xadnekite, K2Ca3[(UO2)(CO3)3]2.8H2O, a new uranyl carbonate mineral from J\xc3\xa1chymov, Czech Republic

[摘要] L\xc3\xadnekite, K2Ca3[(UO2)(CO3)3]2.8H2O, is a new uranyl tricarbonate mineral from J\xc3\xa1chymov, Western Bohemia, Czech Republic. It occurs in association with grimselite, andersonite, liebigite, \xc4\x8dejkaite, schröckingerite, agricolaite, je\xc5\xbeekite and braunerite. L\xc3\xadnekite forms from uranium-rich aqueous solutions and its origin is associated with post-mining processes. L\xc3\xadnekite is orthorhombic, space group Pnnm, with a = 17.0069(5) Å, b = 18.0273(5) Å, c = 18.3374(5) Å and V = 5622.1(2) Å3, and Z = 8. It forms tabular, mostly isometric crystals, up to c. 0.5 mm across, typically in multiple intergrowths. The color is pale olive to khaki green and it has a greenish white to yellowish white streak. Crystals are transparent and have vitreous luster. The Mohs hardness is estimated to be between 2 and 3. L\xc3\xadnekite is brittle with an uneven fracture and perfect cleavage on {100} and very good cleavage on {010}. It exhibits intense greenish yellow luminescence under both short- (254 nm) and long-wave (366 nm) UV radiation. The calculated density is 2.922 g/cm3. The mineral is biaxial (+) with indices of refraction, ? = 1.546(2), ? = 1.550, ? = 1.562(2). The 2Vobs is moderate; the calculated 2V is +60°. Optical orientation: Y = a, X = b, Z = c. The electron microprobe analyses (average of 28) provided: Na2O 0.06, K2O 6.89, CaO 14.11, CuO 0.12, UO3 48.76, CO2* 22.51, H2O* 12.20 (~12.9 from TG) (*calculated), total 104.65 wt%. The empirical formula (based on 30.22 O apfu) is: (K1.73Na0.02)?1.75(Ca2.97Cu0.02)?2.99[(UO2)(CO3)3]2.02(H2O)8.00. The Raman and infrared spectra exhibit prominent features consistent with the mineral being a hydrated uranyl tricarbonate, with fundamental vibrations of H2O molecules, CO32- anions and UO22+ ions. The seven strongest powder X ray diffraction lines are [dobs in Å (hkl) Irel

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